Production of silicon nano-particles and uses thereof

ABSTRACT

A process for producing silicon nano-particles from a raw silicon material, the process including steps of alloying the raw silicon material with at least one alloying metal to form an alloy; thereafter, processing the alloy to form alloy nano-particles; and thereafter, distilling the alloying metal from the alloy nano-particles whereby silicon nano-particles are produced.

TECHNICAL FIELD

The present invention relates to the production of siliconnano-particles as well as components and devices comprising such siliconnano-particles.

BACKGROUND OF THE INVENTION

Silicon nano-particles have a variety of commercial applicationsincluding for instance as a material for the manufacture of solar celldevices and anodic elements of battery devices. Certain methodscurrently used for large-scale production of silicon nano-particlesinvolve the use of vapour deposition or atomization which tend to berelatively costly to implement at scale and such processes also tend toproduce silicon nano-particles having undesirable microstructures whichare unsuitable for solar cell and battery applications. Technologydeveloped by Siemens (i.e. the “Siemens process”) has been used for theproduction of silicon nano-particles which are of suitable purity foruse in solar-cell applications. However, this process is perceived to beboth relatively expensive and non-environmentally-friendly as it isestimated that approximately 200 MW·Hr of electricity is expended inorder to produce 1 ton of solar-grade silicon. Carbothermic reductionprocesses have been developed as a potential alternative to the Siemensprocess, however, these processes do not produce silicon nano-particlesthat are of solar-grade quality since impurities such as boron andphosphorous, which are inherently contained in carbon, cannot be removedto suitably low levels (i.e. to levels in the parts-per-million orparts-per-billion). It would be appreciated that the relatively highcosts associated with producing silicon nano-particles utilising currentcommercial methods also contributes to the overall manufacturing costsfor solar cell and battery device components comprising siliconnano-particles and therefore a perceived need exists to address thisproblem.

It is also perceived that there are shortcomings associated with certaindevices currently available on the market having components comprised ofsilicon nano-particles, apart from the production costs of suchcomponents. Solar cell devices for instance may typically compriserelatively rigid and bulky panel structures which renders themimpractical to store, transport and install such devices. On the otherhand, silicon is finding increasing usage as a substitute material forgraphite in the anodes of rechargeable lithium-ion batteries due to itsability to store a much larger capacity of lithium ions than graphiteduring charging. However, when fully charged, silicon may typicallyexpand to more than 3 times its ordinary volume which tends to break theelectrical contacts within the anode as well as cause cracking in thesilicon material via which moisture may seep into the anode to furthercompromises operation of the anode. One approach to alleviate thisproblem has been to simply charge the battery to only a partial amountof its full capacity to limit the amount of expansion of the silicon inthe anode. Another approach has been to provide a mixture of graphiteand silicon particles in the anodic material in seeking to strike abalance between improving lithium-ion storage capacity (by virtue of thesilicon nano-particles) whilst alleviating the amount of overallexpansion of the anodic material (by virtue of the graphite particleswhich expand to a much smaller extent than silicon). However, suchapproaches tend to make inefficient use of the overall potential storagecapacity of the anodic material in the battery. Accordingly, thereexists a perceived need to address the problem arising from expansion ofsilicon nano-particles in the anodic material of batteries in order toutilise the superior storage capacity of silicon anodic materials.

SUMMARY OF THE INVENTION

The present invention seeks to alleviate at least one of theabove-described problems.

The present invention may involve several broad forms. Embodiments ofthe present invention may include one or any combination of thedifferent broad forms herein described.

In one broad form the present invention provides a process for producingsilicon nano-particles from a raw silicon material, the processincluding steps of:

-   -   (i) alloying the raw silicon material with at least one alloying        metal to form an alloy;    -   (ii) processing the alloy to form alloy nano-particles; and    -   (iii) distilling the alloying metal from the alloy        nano-particles whereby silicon nano-particles are substantially        produced.

Preferably, step (ii) includes forming alloy particles having diametersapproximately in the range of 100-150 nm.

Preferably, step (ii) may include ball milling the alloy to form thealloy nano-particles.

Preferably, step (ii) may be performed in a controlled environment toalleviate oxidisation of the alloy nano-particles. Typically, thecontrolled environment includes a milling chamber in which the alloy isbeing ball milled with at least one of an inert gas, oil, diesel,kerosene, dehydrated ethanol, N-Methyl-2-pyrrolidone (“NMP”) and othersuitable organic solvents disposed in the milling chamber.

Alternatively, the alloy may be in a liquid form and step (ii) mayinclude atomisation of the alloy to form the alloy nano-particles.

Preferably, step (iii) may include distilling the alloying metal fromthe alloy nano-particles in a vacuum furnace.

Preferably, the silicon nano-particles produced in accordance with step(iii) may include diameters of approximately in the range of around 50nm-150 nm diameter. In certain embodiments, a further optional stepfollowing step (iii) may be effected in which the silicon nano-particlesmay be subjected to a further milling process in a controlledenvironment to break apart a porous structure comprised by thenano-silicon particles. Preferably the controlled environment mayinclude filling the milling chamber with dehydrated ethanol.

Preferably, the alloying metal may include at least one of zinc andmagnesium.

In a further broad form, the present invention provides an apparatus forproducing silicon nano-particles from a raw silicon material, theapparatus including:

an apparatus for alloying the raw silicon material with at least onealloying metal to form an alloy;

an apparatus for processing the alloy to form alloy nano-particles; and

an apparatus for distilling the alloying metal from the alloynano-particles whereby silicon nano-particles are produced.

Preferably, the apparatus for processing the alloy to form the alloyparticles may be configured to form alloy nano-particles havingdiameters approximately in the range of 100-150 nm diameter.

Preferably, the apparatus for processing the alloy to form the alloyparticles may include a ball milling apparatus having a milling chamberin which the alloy particles are able to be ball-milled in a controlledenvironment to alleviate oxidisation of the alloy nano-particles and/orexplosion due to pressure build-up within the milling chamber.

Preferably, the apparatus may be configured for subjecting the siliconnano-particles to a milling process in a controlled environment to breakapart a porous structure comprised by the nano-silicon particles.

Typically, the controlled environment may include the milling chamber inwhich the alloy is being ball milled having at least one of an inertgas, oil, diesel, kerosene, dehydrated ethanol, N-Methyl-2-pyrrolidone(“NMP”) and other suitable organic solvents disposed therein.

Alternatively, the apparatus for processing the alloy to form the alloynano-particles may include an apparatus for performing atomisation ofthe alloy when in a liquid form.

Preferably, the apparatus for distilling the alloying metal from thealloy nano-particles to produce the silicon nano-particles may include avacuum furnace.

Preferably, the apparatus for distilling the alloying metal from thealloy nano-particles to produce the silicon nano-particles may beconfigured to produce silicon nano-particles having diameters ofapproximately in the range of around 50 nm-150 nm diameter.

Preferably, the alloying metal may include at least one of zinc andmagnesium.

In another broad form the present invention provides a process forproducing silicon nano-particles from a raw silicon material, theprocess including steps of:

-   -   (i) alloying the raw silicon material with at least one alloying        metal to form alloy ingots;    -   (ii) distilling the alloy ingots to produce porous silicon        ingots; and    -   (iii) processing the porous silicon ingots to form silicon        nano-particles.

Preferably, step (iii) includes milling the silicon ingots to formnano-silicon particles having diameters approximately in the range ofaround 50 nm-150 nm diameter. More preferably, the silicon ingots areprocessed by ball-milling the silicon ingots.

In a further broad form, the present invention provides an apparatus forproducing silicon nano-particles from a raw silicon material, theapparatus including:

an apparatus for alloying the raw silicon material with at least onealloying metal to form alloy ingots;

an apparatus for distilling the alloy ingots to produce porous siliconingots; and

an apparatus for processing the porous silicon ingots to form siliconnano-particles.

Preferably, the apparatus for processing the porous silicon ingots toform silicon nano-particles includes an apparatus for milling thesilicon ingots to form nano-silicon particles having diametersapproximately in the range of 50 nm-150 nm diameter. More preferably,the apparatus includes a ball-milling apparatus.

In another broad form, the present invention provides a solar celldevice for use in converting solar energy to electrical current, thesolar cell device including:

a photosensitive element comprising an n-type layer contiguouslyconnected with a p-type layer at a junction region therebetween, then-type layer and contiguously connected p-type layer of thephotosensitive element being configured such that, in response to thephotosensitive element being exposed to solar energy, free electrons areable to be released by the photosensitive element so as to providecurrent flow through a load device forming an external electricalcircuit between the p-layer and p-layer of the photosensitive element;

wherein said n-type layer and said p-type layer include at least oneelectrically-conductive substrate having silicon nano-particlesdeposited on a surface structure of the at least oneelectrically-conductive substrate.

Preferably, the electrically-conductive substrate may include a flexiblestructure. Also preferably, the electrically-conductive substrate mayinclude a fabric layer comprising electrically-conductive textileelements. Preferably, the electrically-conductive textile elements maybe formed by:

-   -   (i) modifying a surface of the textile elements with a        negatively-charged polyelectrolyte; and    -   (ii) coating the modified surface of the textile element with        metal particles.

Also preferably, the electrically-conductive textile elements may beconfigured to have surface structures formed from a coating of metalparticles that may assist in trapping the silicon nano-particles thatare deposited thereon. By way of example, the electrically-conductivetextile elements may include a dendritic-type and/or a lattice-typesurface structure disposed thereon formed by the coating of metalparticles of the electrically-conductive textile elements which may beconfigured for receiving and/or trapping deposited siliconnano-particles and thereby assist in maintaining the siliconnano-particles on the surface structures of the electrically-conductivetextile elements. Silicon nano-particles may for instance fill up and/orbe trapped within recesses, pockets and faults in the surface structuresof the electrically-conductive textile elements formed by the coating ofmetal particles. Furthermore, a plurality of electrically-conductivetextile elements forming the electrically-conductive fabric may beconfigured to form composite textile elements (e.g. yarns, threads etc),for instance by intertwining the plurality of electrically-conductivetextile elements, and silicon nano-particles deposited on to thecomposite electrically-conductive textile element of the fabric may beboth received and/or trapped within the pockets of the surface structureof each individual textile element and also may be trapped and/orentangled between the surface structures of the intertwined textileelements. Any suitable techniques and processes may be used to form suchsurface structures on the electrically textile elements, for instance,during the process of coating the metal particles on to the natural orsynthetic textile elements and suitably processing the metal particlecoating so as to give rise to the desired surface structurecharacteristics, as described in other embodiments. Also preferably, thesilicon nano-particles may be configured to provide a coating which mayencapsulate the electrically conductive fabric and/or at least some ofthe electrically-conductive textile elements forming the fabric.Preferably, the electrically-conductive substrate may have anapproximate thickness of less than 50 microns in the functional contextof this particular broad form. Alternatively, in other embodiments, itis conceivable that the electrically-conductive substrate may notnecessarily comprise electrically-conductive textile elements formed bydepositing metal particles on to a natural or synthetic textile element,but may instead be formed by molding, drawing, pulling, and/or extrudingelongate metal textile elements from a metal mass.

Preferably, the step (i) may include modifying the surface of thetextile element with a negatively-charged polyelectrolyte by in-situfree radical polymerisation.

Preferably, the negatively-charged polyelectrolyte may include at leastone of poly(methacrylic acid sodium salt) and poly(acrylic acid sodiumsalt).

Preferably, step (i) may includes modifying a silanized surface of atextile element with a negatively-charged polyelectrolyte.

Preferably, the step (ii) may include coating the modified surface ofthe textile element with metal particles by electroless metaldeposition.

Preferably, the metal particles may include at least one of copper andnickel particles.

Preferably, the textile elements may include any suitable natural orman-made fibers or yarns, or, a blend or composite structure thereofcomprising such natural or man-made fibers or yarns. Typically, thetextile elements may include at least one of a polyester, nylon, cotton,silk, viscose rayon, wool, linen yarn or fiber, or any blend orcomposite structure thereof.

Preferably, the electrically-conductive textile elements forming thefabric layer may be woven together.

Preferably, the n-type and p-type layers include doped siliconnano-particles. Alternately, in certain embodiments, the siliconnano-particles may not necessarily need to be doped where for instanceelectron excitation is outsourced.

Preferably, the silicon nano-particles may be produced in accordancewith any one of the broad forms of the present invention describedherein.

Preferably, the silicon nano-particles may be printed or coated on tothe at least one fabric layer to form the n-type and p-type layers.

Preferably, the n-type layer may be disposed on a first fabric layer andthe p-type layer may be disposed on a second fabric layer, said firstand second fabric layers comprising electrically-conductive textileelements.

Preferably, the present invention may include a transparent protectivelayer adjacent to the n-type layer.

Preferably, the present invention may include a transparentelectrically-conductive layer configured for electrical communicationwith the n-type layer.

In a further broad form, the present invention provides a solar celldevice for use in converting solar energy to electrical current, thesolar cell having:

first and second electrically conductive terminals configured forelectrical connection with a load device such that the electricalcurrent is able to flow from the solar cell through the load device topower the load device; and

a current generation module comprising a hole donor element and anelectron donor element configured for generation of the electricalcurrent in response to the current generation module being exposed tosolar energy;

wherein the first electrically-conductive terminal includes a firstelectrically-conductive substrate having silicon nano-particlesdeposited thereon configured to function as the hole donor element, and,the second electrically-conductive terminal includes a secondelectrically-conductive substrate having silicon nano-particlesdeposited thereon configured to function as the electron donor elementof the current generation module.

Preferably, the electrically-conductive substrate may include a flexiblestructure. Preferably, at least one of the first and secondelectrically-conductive substrates may include a fabric layer comprisingelectrically-conductive textile elements. Preferably theelectrically-conductive substrate may have an approximate thickness ofless than 50 microns in the functional context of this particular broadform.

Preferably, the electrically-conductive textile elements may be formedby:

-   -   (i) modifying a surface of the textile elements with a        negatively-charged polyelectrolyte; and    -   (ii) coating the modified surface of the textile element with        metal particles.

Also preferably, the electrically-conductive textile elements may beconfigured to have surface structures formed from a coating of metalparticles that may assist in trapping the silicon nano-particles thatare deposited thereon. By way of example, the electrically-conductivetextile elements may include a dendritic-type and/or a lattice-typesurface structure disposed thereon formed by the coating of metalparticles of the electrically-conductive textile elements which may beconfigured for receiving and/or trapping deposited siliconnano-particles and thereby assist in maintaining the siliconnano-particles on the surface structures of the electrically-conductivetextile elements. Silicon nano-particles may for instance fill up and/orbe trapped within recesses, pockets and faults in the surface structuresof the electrically-conductive textile elements formed by the coating ofmetal particles. Furthermore, a plurality of electrically-conductivetextile elements forming the electrically-conductive fabric may beconfigured to form composite textile elements (e.g. yarns, threads etc),for instance by intertwining the plurality of electrically-conductivetextile elements, and silicon nano-particles deposited on to thecomposite electrically-conductive textile element of the fabric may beboth received and/or trapped within the pockets of the surface structureof each individual textile element and also may be trapped and/orentangled between the surface structures of the intertwined textileelements. Any suitable techniques and processes may be used to form suchsurface structures on the electrically textile elements, for instance,during the process of coating the metal particles on to the natural orsynthetic textile elements and suitably processing the metal particlecoating so as to give rise to the desired surface structurecharacteristics, as described in other embodiments. Also preferably, thesilicon nano-particles may be configured to provide a coating which mayencapsulate the electrically conductive fabric and/or at least some ofthe electrically-conductive textile elements forming the fabric.Preferably, the electrically-conductive substrate may have anapproximate thickness of less than 50 microns in the functional contextof this particular broad form. Alternatively, in other embodiments, itis conceivable that the electrically-conductive substrate may notnecessarily comprise electrically-conductive textile elements formed bydepositing metal particles on to a natural or synthetic textile element,but may instead be formed by molding, drawing, pulling, and/or extrudingelongate metal textile elements from a metal mass.

Preferably, the step (i) may include modifying the surface of thetextile element with a negatively-charged polyelectrolyte by in-situfree radical polymerisation. Preferably, the negatively-chargedpolyelectrolyte may include at least one of poly(methacrylic acid sodiumsalt) and poly(acrylic acid sodium salt).

Preferably, step (i) may include modifying a silanized surface of atextile element with a negatively-charged polyelectrolyte.

Preferably, the step (ii) may include coating the modified surface ofthe textile element with metal particles by electroless metaldeposition.

Preferably, the metal particles may include at least one of copper andnickel particles.

Preferably, the textile elements may include any suitable natural orman-made fiber or yarn, or combination thereof.

Preferably, the textile elements may include at least one of apolyester, nylon, cotton, silk, viscose rayon, wool, linen yarn orfiber.

Preferably, the electrically-conductive textile elements forming thefabric layer may be woven together.

Preferably, the silicon nano-particles may be produced in accordancewith any one of the processes described herein.

Preferably, the silicon nano-particles may be deposited on to the atleast one fabric layer.

Preferably, the first electrically-conductive terminal may be formedfrom a first fabric layer comprising electrically-conductive textileelements, and the second electrically conductive-terminal is formed froma second fabric layer comprising electrically-conductive textileelements.

Preferably, the present invention may include a transparent protectivelayer.

In a further broad form, the present invention provides a method ofproducing an electrically-conductive textile element including the stepsof:

-   -   (i) modifying a surface of a textile element with a        negatively-charged polyelectrolyte; and    -   (ii) coating the modified surface of the textile element with        metal particles.

Preferably, the step (i) may include modifying the surface of thetextile element with a negatively-charged polyelectrolyte by in-situfree radical polymerisation.

Preferably, the negatively-charged polyelectrolyte may include at leastone of poly(methacrylic acid sodium salt) and poly(acrylic acid sodiumsalt).

Preferably, the step (i) may include modifying a silanized surface of atextile element with a negatively-charged polyelectrolyte.

Preferably, the step (ii) may include coating the modified surface ofthe textile element with metal particles by electroless metaldeposition.

Preferably, the metal particles may include at least one of copper andnickel particles.

Preferably, the textile elements may include any suitable natural orman-made fibers or yarns, or, a blend or composite structure of any suchnatural or man-made fibers or yarns configured for being formed into afabric.

Typically, the textile elements may include at least one of a polyester,nylon, cotton, silk, viscose rayon, wool, linen yarn or fiber, or anyblend or composite structure thereof.

In a further broad form, the present invention provides an apparatus forproducing an electrically-conductive textile element including:

an apparatus for modifying a surface of a textile element with anegatively-charged polyelectrolyte; and

a coating apparatus for coating the modified surface of the textileelement with metal particles.

Preferably, the apparatus for modifying the surface of the textileelement with the negatively-charged polyelectrolyte may be configured tomodify the surface of the textile element with a negatively-chargedpolyelectrolyte by in-situ free radical polymerisation.

Preferably, the negatively-charged polyelectrolyte may include at leastone of poly(methacrylic acid sodium salt) and poly(acrylic acid sodiumsalt).

Preferably, the apparatus for modifying the surface of the textileelement with the negatively-charged polyelectrolyte may be configured tomodify a silanized surface of a textile element with anegatively-charged polyelectrolyte.

Preferably, the coating apparatus may be configured to coat the modifiedsurface of the textile element with metal particles by electroless metaldeposition.

Preferably, the metal particles may include at least one of copper andnickel particles.

Preferably, the textile elements may include any suitable natural orman-made fibers or yarns, or, a blend or composite structure of any suchnatural or man-made fibers or yarns.

Typically, the textile elements may include at least one of a polyester,nylon, cotton, silk, viscose rayon, wool, linen yarn or fiber, or anyblend or composite structure thereof.

In a further broad form, the present invention provides anelectrically-conductive textile element produced in accordance with themethod steps of the first broad form of the present invention.

In a further broad form, the present invention provides a fabric formedfrom at least one textile element wherein the at least one textileelement is produced in accordance with the method steps of any one ofthe broad forms of the present invention. Typically, the fabric may havean approximate thickness of less than 100 microns.

In a further broad form, the present invention provides a battery deviceincluding an anode element comprising an electrically-conductivesubstrate having a surface structure formed by a coating of metalparticles that is configured for trapping silicon nano-particlesdeposited thereon. Preferably, the silicon nano-particles may be adaptedto encapsulate the surface structure of the electrically-conductivesubstrate. By way of example, the electrically-conductive textileelements of the substrate may include a dendritic-type and/or alattice-type surface structure disposed thereon formed by the metalparticles of the electrically-conductive textile elements which may beconfigured for receiving and/or trapping deposited siliconnano-particles and thereby assist in retaining the siliconnano-particles on the surface structures of the electrically-conductivetextile elements. Silicon nano-particles may for instance fill up and/orbe trapped within recesses, pockets and faults in the surface structuresof the electrically-conductive textile elements formed by the coating ofmetal particles. Furthermore, a plurality of electrically-conductivetextile elements forming the electrically-conductive fabric may beconfigured to form composite textile elements (e.g. yarns, threads etc),for instance by intertwining the plurality of electrically-conductivetextile elements, and silicon nano-particles deposited on to thecomposite electrically-conductive textile element of the fabric may beboth received and/or trapped within the pockets of the surface structureof each individual textile element and also may be trapped and/orentangled between the surface structures of the intertwined textileelements. Any suitable techniques and processes may be used to form suchsurface structures on the electrically textile elements, for instance,during the process of coating the metal particles on to the natural orsynthetic textile elements and suitably processing the metal particlecoating so as to give rise to the desired surface structurecharacteristics, as described in other embodiments. Also preferably, thesilicon nano-particles may be configured to provide a coating which mayencapsulate the electrically conductive fabric and/or at least some ofthe electrically conductive textile elements forming the fabric.Preferably, the electrically-conductive substrate may have anapproximate thickness of less than 100 microns.

Preferably, the electrically-conductive substrate may include a flexiblestructure.

Preferably, the electrically-conductive substrate may include a fabriclayer comprising electrically-conductive textile elements.

Preferably, the electrically-conductive textile elements of theelectrically-conductive substrate may be formed by:

-   -   (i) modifying a surface of the textile elements with a        negatively-charged polyelectrolyte; and    -   (ii) coating the modified surface of the textile element with        metal particles.

Preferably, the step (i) may include modifying the surface of thetextile element with a negatively-charged polyelectrolyte by in-situfree radical polymerisation.

Preferably, the negatively-charged polyelectrolyte may include at leastone of poly(methacrylic acid sodium salt) and poly(acrylic acid sodiumsalt).

Preferably, step (i) may include modifying a silanized surface of atextile element with a negatively-charged polyelectrolyte.

Preferably, the step (ii) may include coating the modified surface ofthe textile element with metal particles by electroless metaldeposition.

Preferably, the metal particles may include at least one of copper andnickel particles.

Preferably, the textile elements may include any suitable natural orman-made fiber or yarn, or combination thereof.

Typically, the textile elements may include at least one of a polyester,nylon, cotton, silk, viscose rayon, wool, linen yarn or fiber, or anyblend or composite structure thereof.

Preferably, the electrically-conductive textile elements forming thefabric layer may be woven together.

Preferably, the silicon nano-particles may be produced in accordance anyone of the broad forms of the present invention described herein.

Preferably, a supersonic beam may be utilised during the deposition ofthe silicon nano-particles on to the electrically-conductive substrate.

In a further broad form, the present invention provides an anode elementfor use in a battery device according to any one of the broad forms ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thefollowing detailed description of a preferred but non-limitingembodiment thereof, described in connection with the accompanyingdrawings, wherein:

FIG. 1 is a schematic illustration of a process of preparingelectrically-conductive cotton yarns via in-situ free radicalpolymerization in accordance with an embodiment of the presentinvention;

FIG. 2 depicts an exemplary copper-coated cotton yarn fabricated inaccordance with the method depicted in FIG. 1;

FIG. 3 depicts a representation of Fourier transform infraredspectroscopy (FTIR) spectra data in respect of pristine cotton yarns,silane-modified cotton, and PMANa-modified cotton yarns formed inaccordance with an embodiment of the present invention;

FIG. 4 depicts a representation of EDX spectrum of PMANa-modified cottonproduced in accordance with an embodiment of the present invention;

FIG. 5 depicts SEM images representing surface morphologies of cottonfibers with different modifications including (A) pristine cotton; (B)silane-modified cotton; (C) PMANa-coated cotton; (D-F) copper-coatedcotton in accordance with an embodiment of the present invention;

FIG. 6 depicts data representing (A) linear resistance of theas-synthesized copper-coated cotton yarns and (B) Tensile strength ofthe cotton yarns produced in accordance with an embodiment of thepresent invention;

FIG. 7 depicts process steps for fabrication of a woven fabric formedfrom copper-coated yarns produced in accordance with an embodiment ofthe present invention;

FIG. 8 depicts sheet resistance data of fabrics woven from copper-coatedyarns produced in accordance with an embodiment of the presentinvention;

FIG. 9 depicts SEM images of cotton yarns unraveled from washed fabricsunder different washing times, the cotton yarns being produced inaccordance with an embodiment of the present invention;

FIG. 10 depicts a PMANa-assisted nickel-coated cotton fabric produced inaccordance with an embodiment of the present invention;

FIG. 11A depicts an exemplary PAANa-assisted copper-coated yarn formedin accordance with an embodiment of the present invention;

FIG. 11B depicts an exemplary PAANa-assisted nickel-coated silk yarnformed in accordance with an embodiment of the present invention;

FIG. 12A depicts PAANa-assisted copper-coated nylon yarn produced inaccordance with an embodiment of the present invention; and

FIG. 12B depicts a polyester fabric formed from PAANa-assistedcopper-coated nylon yarn produced in accordance with an embodiment ofthe present invention.

FIG. 13 shows a flowchart of process steps in accordance with anembodiment of the present invention for use in producing siliconnano-particles from a raw silicon material;

FIG. 14 shows a functional block diagram of an exemplary apparatus foruse in performing process steps in accordance with embodiments of thepresent invention to produce silicon nano-particles from a raw siliconmaterial;

FIG. 15 shows a top view and magnified view of an example fabriccomprising inter-woven electrically-conductive yarns (e.g. copper coatedcotton yarns), the fabric having silicon nano-particles printed orcoated thereon for application as a p-type or n-type layer of a solarcell;

FIG. 16 shows a cross-sectional view of a basic solar cell devicestructure manufactured in accordance with an embodiment of the presentinvention;

FIG. 17 shows a cross-sectional view of a preferred embodiment solarcell device structure manufactured in accordance with an embodiment ofthe present invention wherein p-type and n-type layers are printed orcoated on first and second electrically-conductive fabric layersrespectively; and

FIG. 18 shows a cross-sectional view of another preferred embodimentsolar cell device structure manufactured in accordance with anembodiment of the present invention wherein p-type and n-type layers areprinted or coated on a single electrically-conductive fabric layer.

FIGS. 19-22 shows examples of silicon nano-particles encapsulating andbeing trapped by on a surface structure of an electrically-conductivetextile element of a fabric as used in applications such as solar cellsdevices and as an anode element of a battery device.

FIGS. 23A-23B depicts basic functional diagrams of a battery deviceduring charging and discharging cycles.

FIG. 24 shows an SEM image of an electrically-conductive textile element(e.g. a fiber or thread) which may be used to form anelectrically-conductive substrate (e.g. a fabric layer), and theelectrically-conductive textile element including a dendritic-typecopper-coated surface structure having “pockets” within which siliconnano-particles deposited on to the surface may be trapped/entangled.

FIG. 25 shows an SEM image of an electrically-conductive textile element(e.g. a fiber or thread) which may be used to form anelectrically-conductive substrate (e.g. a fabric layer), and theelectrically-conductive textile element including a lattice-typecopper-coated surface structure having “pockets” within which siliconnano-particles deposited on to the surface may be trapped/entangled.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Exemplary embodiments of the present invention will now be describedwith reference to the FIGS. 1 to 25.

Referring firstly to FIG. 1, a procedure for preparing PMANapolyelectrolytes on textile substrates such as cotton yarn isillustrated schematically. The embodiment involves an in-situ freeradical polymerization method which may be performed upon cotton yarnsby way of example to prepare poly(methacrylic acid sodium salt)(PMANa)-coated cotton yarns. Subsequent ion exchange, ion reduction andelectroless deposition of metal particles onto the PMANa-coated cottonyarns may then be performed in order to yield electrically-conductivecotton yarns of suitable quality for production on a commercial scale.It should be noted that this embodiment may also be applicable to thepreparation of PAANa polyelectrolytes on textile substrates.

In performing the process, cotton yarns are first immersed in a solutionof 5-20% (v/v) C═C bond bearing silane for approximately 30 minutes soas to allow the hydroxyl groups of cellulose to suitably react with thesilane molecules. The cotton yarns are then rinsed thoroughly with freshdeionized (DI) water so as to remove any excess physical adsorbed silaneand by-product molecules. This step of silanisation is represented by(100) in FIG. 1.

The rinsed cotton yarns are then placed into an oven at 100-120° C. forbetween approximately 15-30 minutes to complete the condensationreaction. Subsequently, the silane-modified cotton yarns are immersedinto approximately 50 mL aqueous solution comprising of 3-7 g of MANapowder and 35-75 mg of K2S2O8 (similarly, AANa powder may be used inrespect of PAANa polyelectrolytes). The whole solution mixture withcotton yarns is heated at 60-80° C. in an oven for 0.5-1 hour in orderto carry out the free radical polymerization. In the free radicalpolymerization process, the double bond of silane can be opened by thefree radicals resulting in the growth of PMANa polyelectrolyte onto thecotton fiber surface. This step of free radical polymerisation isrepresented by (110) in FIG. 1.

Thereafter, the PMANa-coated cotton yarns are immersed into a 39 g/Lcopper(II) sulphate pentahydrate solution for 0.5˜1 hour, where the Cu2+ions are immobilized onto the polymer by ion exchange. Followed byreduction in 0.1-1.0 M sodium borohydride solution, Cu2+ will be reducedto Cu particles which act as nucleation sites for the growth of Cu inthe subsequent electroless deposition of Cu. This step of ion exchangeand reduction is represented by (120) in FIG. 1.

The polymer-coated cotton after reduction in sodium borohydride solutionis immersed in a copper electroless plating bath consisting of 12 g/Lsodium hydroxide, 13 g/L copper(II) sulphate pentahydrate, 29 g/Lpotassium sodium tartrate, and 9.5 mL/L formaldehyde in water for 60-180minutes. The as-synthesized Cu-coated yarns are rinsed with deionized(DI) water and blown dry. The step of performing electroless metaldeposition is represented by (130) in FIG. 1 and an exemplary Cu-coatedcotton yarn produced in accordance with the methods steps of this firstembodiment is represented by (200) in FIG. 2.

The silane-modified cotton and PMANa-grafted cotton are able to becharacterized by Fourier transform infrared spectroscopy (FTIR). Asshown in FIG. 3, the presence of additional peaks located at 1602 and1410 cm-1 represent C═C bonds in the silane molecules. Anotherdistinctive peak located at 769 cm-1 is attributed to Si—O—Si symmetricstretching, indicating that the silane molecules are successfullycross-linked with each other on the cotton fiber surface. For thePMANa-modified cotton sample, a new peak located at 1549 cm-1 standingfor carboxylate salt asymmetrical stretching vibrations confirm thePMANa grafting. Other peaks located at 1455 and 1411 cm-1 are bothattributed to carboxylate salt symmetrical stretching vibrations fromthe PMANa.

The PMANa-grafted cotton is also able to be characterized byenergy-dispersive X-ray spectroscopy (EDX). It is shown in FIG. 4 thatpolymerization of MANa leaves the cotton sample with a sodium elementwhich indicates the presence of PMANa. Referring further to the FIG. 5scanning electron microscopy (SEM) image, no obvious difference betweenthe morphology on the surfaces of silanized cotton fiber surface and theraw cotton fiber surfaces may be visibly evident. However, afterpolymerization of PMANa upon the silanized cotton fiber surface, it isnotable that a layer of coating had been wrapped on the cotton fibersurface. FIGS. 5D-F show that the copper metal particles are depositedrelatively evenly, without any signs of cracks.

The conductivity of the copper-coated cotton yarns is able to becharacterized by a two-probe electrical testing method. In this regard,linear resistance of the copper-coated yarns in the fabrication is foundto be ˜1.4 Ω/cm as shown in FIG. 6A, and with superior tensileproperties compared to the untreated cotton yarns, with both increase intensile extension (+33.6%) and maximum load (+27.3%) as shown in FIG.6B. The increase in tensile extension and maximum load is perceived tobe due to the reinforcement on the strength of cotton yarns by a layerof copper.

To further test the adhesion of the copper on the cotton yarn surfaceand the washing durability, the copper-coated cotton yarns are firstwoven into a fabric first. As-synthesized copper-coated cotton yarnsshown in FIG. 7A are firstly wound upon a cone as shown in FIG. 7B byuse of an industrial yarn winder. Thereafter, the cone is transferred toa CCI weaving machine as shown in FIG. 7C whereby the copper-coatedyarns are woven into a fabric. In the weaving setting, the copper-coatedcotton yarns are configured to form the wefts of the fabric while thewarps of the fabric are formed by the untreated cotton yarns as shown inthe inset image of FIG. 7D which are initially mounted on the weavingmachine. No problems or defects are found in the weaving process. Afterweaving, the fabric is cut into pieces of 5 cm×15 cm and overlocked atthe four edges as shown in FIG. 7D, and subsequently, subjected to aseries of washing cycles according to the testing standard AATCC TestMethod 61—Test No. 2A: Colorfastness to Laundering, Home and Commercial:Accelerated (Machine Wash) (FIG. 7E) under following washing conditions:

-   -   Washing Temperature 49±2° C.    -   Volume of DI Water 150 mL    -   No. of Steel Balls added 50 pcs    -   Time of Washing 45 minutes

It should be noted that according to the testing standard, 1 washingcycle is equivalent to approximately 5 commercial machine launderingcycles. In total, 6 washing cycles are conducted, which accordingly, isconsidered to equate to approximately 30 commercial machine launderingcycles. Changes in the electrical resistance of the washed fabrics areable to be evaluated using a four-probe method whereby the sheetresistances of the fabrics produced in accordance with this embodimentare measured to be 0.9±0.2 ohm/sq (unwashed), and 73.8±13.4 ohm/sq afterthe fourth wash which is equivalent to approximately 20 commercialmachine laundering cycles as shown in FIG. 8.

The surface morphology of the washed copper-coated cotton yarns are ableto be characterized by unraveled the washed copper-coated cotton yarnsfrom the fabric and examined under an SEM. As shown in the SEM images ofFIG. 9, it is visibly evident that the copper metal particles areretained on the surface of the cotton fibers. One perceived reason forthe increase in sheet resistance is due to the loosened structure of thecotton fibers arising from repeated washing cycles.

It is also noted that during application of the standard washing cycleto the produced fabric, 50 pieces of steel balls are added into thewashing canisters in seeking to simulate vigorous rubbing and stretchingforces of a laundering machine. The abrasion of the steel balls on thefabric impacts substantially upon the fiber structure. As thecopper-coated cotton fibers are no longer held in a tightened manner itis perceived that they lose contact with each other so as to reduceelectrically-conductive pathways available for the movement ofelectrons. Accordingly, the sheet resistance increases upon repeatedwashing cycles notwithstanding, the SEM images in FIG. 9 which confirmthe relatively strong adhesion of copper metal particles on the cottonfiber surface.

In alternate embodiments of the present invention, rather than coatingthe cotton fibers with copper particles, nickel metal particles mayinstead be electrolessly plated on to the textile surface by using thesame approach described above. Same experimental procedures and testingmay be conducted however the source of nickel that may be utilised is120 g/L nickel(II) sulphate solution in the ion exchange procedure.Subsequently an electroless nickel plating bath is utilised consistingof 40 g/L nickel sulphate hexahydrate, 20 g/L sodium citrate, 10 g/Llactic acid, and 1 g/L dimethylamine borane (DMAB) in water for 60-180minutes. The sheet resistance of the resulting nickel-coated cottonfabric is found to exhibit substantially similar results as that of thecopper coated fiber yarns as shown in FIG. 8. Turning to FIG. 10, anexemplary nickel-coated cotton fabric is represented by (300) whichexhibits a high degree of evenness of nickel metal, with bulk resistancemeasured as 3.2Ω.

It will be appreciated that other embodiments of the present inventionmay involve the use of substrates other than cotton and could besuitably applied to various textile materials formed from natural orman-made yarn or fiber including for instance polyester, nylon, cotton,silk, viscose rayon, wool, linen yarns, fibers or combinations thereof.In this regard, an exemplary PAANa-assisted copper-coated yarn producedin accordance with an embodiment of the present invention is shownrepresented by (400) in FIG. 11A, an exemplary PAANa-assistednickel-coated silk yarn produced in accordance with an embodiment of thepresent invention is shown represented by (500) in FIG. 11B, anexemplary PAANa-assisted copper-coated nylon yarn produced in accordancewith an embodiment of the present invention is shown represented by(600) in FIG. 12A, and, an exemplary polyester fabric formed fromPAANa-assisted copper-coated nylon yarn produced in accordance with anembodiment of the present invention is represented by (700) in FIG. 12B.

It will be appreciated from the preceding summary of the broad forms ofthe invention that various advantages may be conveniently providedincluding electrically-conductive textile elements may be produced whichmay be suitably flexible, wearable, durable and/or washable forintegration into a textile/fabric. Moreover, such high performanceelectrically-conductive textile elements (fibers, yarns and fabrics) maybe produced utilising relatively low-cost technology cost-effectively ona mass scale based upon the chemical reaction of in-situ free radicalpolymerization to grow negatively-charged polyelectrolytes such as PMANaor PAANa on textile substrates which may conveniently provide animproved negatively-charged polyelectrolyte layer bridging theelectrolessly deposited metal and textile elements and substrates.Notably, the adhesion of electrically-conductive metal to textilesubstrates may be greatly improved by such surface modification of alayer of negatively-charged polyelectrolyte PMANa or PAANa, in which theelectrical performance of such electrically-conductive textiles may bemore reliable, robust and durable under repeated cycles of rubbing,stretching, and washing. Also, the in-situ free radical polymerizationmethod used to prepare the negatively-charged polyelectrolyte may beperformed under ambient and aqueous conditions without using any strongchemicals.

In another embodiment, a process and apparatus is provided which areused to produce silicon nano-particles from a raw silicon material.Different grades of raw silicon material may be utilised depending uponthe purity of the silicon nano-particles that are required for aparticular application. If the purity of the silicon nano-particlesproduced is of particular concern, for instance where the siliconnano-particles are to be used in solar panels, then a solar gradesilicon raw material may be suitably used. If purity is not ofparticular concern, for instance if the silicon nano-particles areintended to be used for production of anodic or cathodic materials inbatteries, then a metallurgical grade silicon raw material may insteadbe suitably used.

Referring now to the process steps shown in FIG. 13 and the apparatus(900) shown in FIG. 14, the raw silicon material is firstly alloyed withany alloying metal that is able to be distillable from the alloy usingan alloying apparatus (910), for instance magnesium or zinc. This stepis represented by block 800 in FIG. 13. However, in these embodiments,the alloying metal which in is used is magnesium. The process ofalloying the magnesium with the raw silicon material is performed undera vacuum conditions or otherwise in a controlled environment sincemagnesium is extremely flammable at high temperatures. The alloy isformed in proportions of approximately 53% (atomic percent) silicon and47% magnesium. A lower percentage of silicon may be used in forming thealloy however the efficiency of the process is observed to lowersignificantly going forward. However, this ratio can be used to controlthe size of the final nano-silicon. Zinc, or a combination of bothmagnesium and zinc, may also be used as the alloying metal in otherembodiments as the alloying metal as the metals are distillable in bothsituations. Once formed, the alloy will typically be in the form ofingots.

Any suitable processing step may be employed to break the alloy ingotsinto alloy particles of approximately in the range of around 100 nm-150nm in diameter. This step is represented by block 810 in FIG. 13. Inthis embodiment, the alloy ingots are broken down in to alloynano-particles in a ball milling apparatus (920). A controlled medium isused during the step of ball milling the alloy ingots into thenano-particles to alleviate oxidisation during the ball milling processwhich if milled in an uncontrolled medium may in an extreme scenarioresult in an explosion, and/or, may affect the integrity of the siliconnano-particles as silicon will be oxidised. To provide such a controlledmedium, the milling chamber may for instance be filled with an inertgas, oil, diesel, or kerosene, dehydrated ethanol (i.e. all organicoils/surfactants/solvents), N-Methyl-2-pyrrolidone (“NMP”), othersuitable organic solvents, or any combination thereof to alleviate riskof oxidisation arising. It should be noted that if the siliconnano-particles to be produced in accordance with this embodiment are tobe used in application such as solar panels where purity is relativelysolar purposes, oils should not be used to fill the milling chamber asthe milling medium. Instead, the milling medium is a vacuum either,filled with Argon gas, or filled with dehydrated ethanol. Preferablydehydrated ethanol may conveniently be used as this will serve as aprotective medium during the transit of the alloy nano-particle powdersfrom the milling chamber to a distillation chamber where the alloynano-particles will subsequently undergo distillation to remove thealloying metal(s) from the alloy nano-particles.

In alternate embodiments, it may be possible to form the alloynano-particles from the alloy when in the form of a liquid solution byuse of a metallurgical atomisation process. Conveniently, in accordancewith this process, the particle size of the alloy nano-particles areable to be suitably controlled. The process of forming the alloynano-particles is a relatively more costly process, however the step ofdistillation during the entire production process may also serve as anannealing cycle, hence growing grains in the amorphous particles, whichmay result in production of silicon nano-particles of suitableperformance for use in solar cell applications.

After forming the alloy nano-particles of approximately in the range ofaround 100 nm-150 nm in diameter by utilizing either ball-milling oratomisation processes, the alloying metal(s) are distilled from thealloy nano-particles using a distillation apparatus (930) so thatsilicon nano-particles of approximately in the range of around 50 nm-150nm in diameter remain. This step is represented by block 820 in FIG. 13.The distillation process is performed by transferring the alloynano-particles in to a vacuum furnace. Where the alloy ingots have beenballed-milled in a milling chamber with an oil filling the millingchamber as the milling medium, the oil that has been transferred withthe alloy nano-particles from the milling chamber into the vacuumfurnace will first be evaporated or ‘burnt’ at a temperature ofapproximately around 460° C. The temperature in the vacuum furnace isthen raised to around approximately 760° C. at 6 Pa vacuum in order todistill the alloying metal from the alloy nano-particles. The varying oftemperatures in the vacuum chamber may assist in increasing surface areaof the resulting nano-particles which may be useful in both solar cellapplications as well as applications where the silicon nano-particlesare used to provide anodic or cathodic material for batteries. Thesilicon nano-particles resulting after the vacuum furnacing step isperformed are of approximately in the range of 50 nm-150 nm in diameterdue to the mass and weight difference of magnesium and Si. In certainembodiments, a further optional step following distillation may beeffected in which the silicon nano-particles may be subjected to afurther milling process in a controlled environment to break apart aporous structure comprised by the nano-silicon particles. Preferably thecontrolled environment may include filling the milling chamber withdehydrated ethanol. In certain embodiment, this step will differ in thatthe ingots are processed to be of the same size to eliminate variationsof the quality of distillation. The step of distillation advantageouslycreates pores within the silicon nano-particles and by using differentpercentages of Mg or Zn (as example, distillable metals) in the alloy,it is possible to control the porosity of the final nano-particlesproduced as exemplified by the SEM and BET images/data drawings. Thesepores in the surfaces of the silicon nano-particles may be particularlyuseful in applications where the silicon nano-particles are used to formthe anodic or cathodic material of battery devices. That is, these poresmay assist in reducing expansion of the anodic or cathodic materialduring charging and discharging of the battery. The ability tocontrollably produce the pores on the surfaces of the siliconnano-particles is also advantageous in that the presence of such poresprovides additional stiffness to an anodic or cathodic structure formedfrom such nano-particles. This is analogous to the way in which anI-beam provides relatively greater structural stiffness than a regularblock of steel due to its structure.

In an alternate embodiment, the process of producing siliconnano-particles from a raw silicon material may involve a differentsequence of processing steps to that as described above. The raw siliconmaterials is firstly alloyed with an alloying metal such as magnesium orzinc to form alloy ingots. The alloy ingots are distilled to produceporous pure silicon ingots which are then ball-milled to produce siliconingots approximately in the range of around 50 nm-150 nm in diameter.Before the alloy ingots are distilled, the ingots may first be processedto form pellets of around 1 cm in diameter. The silicon nano-particlesof approximately in the range of around 50 nm-150 nm in diameter areproduced by this process may be utilised for instance in applications asa anodic or cathodic material of a battery. Such anodic or cathodicmaterial may comprise a flexible fabric upon which the siliconnano-particles are coated or otherwise bonded to, or, may be mixed witha conventional carbon-based anode.

In a further embodiment of the present invention, a solar cell device isprovided for converting solar energy to electricity. FIG. 16 shows abasic functional structure of a solar cell device manufactured inaccordance with an embodiment of the present invention comprising aphotosensitive element having an n-type layer contiguously connectedwith a p-type layer at a junction region therebetween. The n-type layerand contiguously connected p-type layer of the photosensitive elementare configured so that, when solar energy in the form of photons (1130)bombard the n-type layer of the photosensitive element, the energy ofthe photons frees electrons in the lower p-type layer which may thencross the junction region to the n-type layer and flow through a loaddevice forming an external electrical circuit between the p-layer andn-layer of the photosensitive element. Electrically-conductive terminals(1100,1110) are also disposed on the n-type layer and the p-type layerto which the load device (1120) may be connected to form the externalelectrical circuit between the n-type and p-type layers. In certainembodiments, the electrically-conductive terminals (1100,1110) maycomprise a layer of aluminium.

Referring now to FIG. 17, a preferred embodiment of a solar cell deviceis shown in which the n-type layer (1210) and the p-type layer (1220)are formed from a first fabric layer and a second fabric layerrespectively having silicon nano-particles thereon using any suitabledeposition technique. The first and second fabric layers are comprisedby electrically-conductive synthetic or non-synthetic yarns (or anyblend or composite structure thereof) that have been inter-woventogether in accordance with any of the embodiments described above.Advantageously, the deposited silicon nano-particles are trapped withina surface structure of the electrically-conductive textile elementswhereby the surface structure may include a dendritic-type orlattice-type structure having “pockets” formed by a coating of metalparticles that are suited for being filled up by and trapping thesilicon nano-particles therein. Furthermore, the silicon nano-particlesmay encapsulate the surface structure of the electrically-conductivetextile elements. FIG. 19 shows an example of how a fabric layer formedfrom electrically-conductive fibres (1401) may be encapsulated by a massof silicon nano-particles (1400) deposited on the fabric layer. FIG. 20further shows an example of how silicon nano-particles deposited on thestructure of the fabric layer may be entangled within the structure oftwo different kinds of electrically-conductive textile fibres(1501,1502) woven together to form the fabric layer. FIG. 21 shows afurther example of how two different textile thread structures may beconfigured to form a helical type structure within which siliconnano-particles deposited thereon may conveniently encapsulate and/or beentangled within the structure. FIG. 22 shows a further example inclose-up view of textile elements of varying diameters being wrappedabout each other to form a first composite thread (1701), textileelements of varying diameters being wrapped about each other to form asecond composite thread (1702), and the first and second compositethreads (1701,1702) further being configured to be intertwined aroundeach other to form a helical type configuration. Silicon nano-particlesmay be conveniently entangled within or encapsulate the structures ofthe individual composite threads (1701,1702) themselves, or, may beentangled within or encapsulate the overall helical type configurationcomprising the first and second composite threads (1701,1702). Returningto the present example, the copper coating of theelectrically-conductive yarns of the electrically-conductive first andsecond fabric layers may include dendritic structures (e.g. such asshown in the SEM image “F” of FIG. 5) whereby the silicon nano-particlesthat are deposited on to the first and second fabric layers mayconveniently rest within the “pockets” of the dendritic structures.FIGS. 24 and 25 further depict SEM images of electrically-conductivetextile elements (e.g. a fiber or thread) which may be used to form anelectrically-conductive substrate (e.g. a fabric layer), wherein the andthe electrically-conductive textile elements can be seen to include adendritic-type surface and lattice-type copper-coated surface structurerespectively having “pockets” within which silicon nano-particlesdeposited on to the surfaces may be trapped/entangled.

A supersonic deposition technique may be employed to assist in thedeposited silicon nano-particles penetrating and being trapped withinthe pockets of the surface structure of the yarns and fibers of thefabric layers. FIG. 15 shows an exemplary electrically-conductive fabricstructure formed for instance from interwoven copper-coated cottonyarns. A section of the fabric is shown in magnified view with siliconnano-particles printed or coated uniformly on to the surface of thefibers which form the fabric structure. The silicon nano-particlesdeposited on to the fabric layers are suitably doped with impurities soas to provide the n-type or p-type characteristics of the respectivelayers. Conveniently, the copper-coated first and secondelectrically-conductive fabric layers not only provide a flexiblestructure for formation of the n-type and p-type layers (1210,1220) butmay also provide dual functions as the electrically-conductive terminalsof the n-type and p-type layers (1210,1220) without requiring additionalelectrically-conductive terminals, films or contacts to be fabricatedupon the n-type and p-type layers (1210,1220). Protective layers mayalso be formed adjacent to surfaces of the n-type layer and p-type layer(1210,1220) to provide these layers with protection from damage. Theprotective layer formed adjacent the n-type layer is formed from asuitably flexible transparent material such as ethylene-vinyl acetate(EVA) type material or the like so that this does not restrict photonsfrom contacting with the photosensitive element. The dimensions andproperties of any protective layers that are formed adjacent the n-typelayer or p-type layer will be suitably selected so as to not comprisethe working spectrum of light that may be incident upon these layers.

In another preferred embodiment, the solar cell device may be formed ona single fabric layer as shown in FIG. 18. The fabric layer includes athickness of approximately 50 microns or less. As in the example above,the fabric layer is also comprised by electrically-conductive syntheticor non-synthetic yarns that have been inter-woven together. In thisembodiment, the fabric layer is firstly coated with p-type siliconnano-particles of solar grade purity so as to form the p-type layer(1340) of the photosensitive element of the solar cell. Then on a firstsurface of the p-type layer (1340), n-type silicon nano-particles areprinted or coated thereon to form the n-type layer (1330) of thephotosensitive element. A transparent electrically-conductive oxidelayer (1320) is then formed on a surface of the n-type layer (1330) soas to sandwich the n-type layer (1330) between it and the p-type layer(1340). The transparent electrically-conductive oxide layer (1320)serves as the electrically-conductive terminal of the n-type layer(1330) whilst the electrically-conductive fabric serves as theelectrically-conductive terminal of the p-type layer (1340). A loaddevice when connected between these two electrically-conductiveterminals forms an external electrical circuit via which electriccurrent may flow between the n-type and p-type layers (1330,1340) whenthe photosensitive element is bombarded by photons. A transparentprotective layer (1310) formed from EVA is also formed on thetransparent electrically-conductive oxide layer (1320) as shown toprotect the oxide layer from damage. A protective layer (1350) issimilarly formed on the p-type layer (1340) as shown in FIG. 18.

In the above-described solar cell device embodiments, the siliconnano-particles that are used are produced in accordance with siliconnano-particle production processes of embodiments described herein.However, it would be understood that silicon nano-particles produced inaccordance with any other process may also be used. Furthermore, inalternate embodiments the n-type and p-type layers may be formed fromother suitably doped n-type and p-type nano-particles, not necessarilybeing silicon nano-particles.

In alternate embodiments of the present invention in which a solar celldevice is provided comprising silicon nano-particles, the solar celldevice may not require the silicon nano-particles to be doped to form ap-layer, an n-layer and a p/n junction region therebetween. In suchalternate embodiments, the solar cell includes a current generationmodule comprising a hole donor element and an electron donor elementconfigured for generation of the electrical current in response to thecurrent generation module being exposed to solar energy. The firstelectrically-conductive terminal includes an electrically-conductivesubstrate having silicon nano-particles disposed thereon configured tofunction as the hole donor element, and, the secondelectrically-conductive terminal includes an electrically-conductivesubstrate having silicon nano-particles disposed thereon configured tofunction as the electron donor element of the current generation module.When excited by exposure to solar energy, the first and secondelectrically-conductive terminals having the silicon nano-particlesdisposed thereon are configured to suitably function as the hole donorand electron donor respectively for generation of the electrical currentof the solar cell device.

In yet a further embodiment of the present invention, a battery deviceis provided as shown in the basic functional diagram of FIG. 16. Incontrast to certain traditional battery devices which utilise a carbonmaterial as the anode to assist in effecting energy storage, in thisembodiment, the anode element comprises an electrically-conductivesubstrate (which for example may be a copper-coated fabric) upon whichis deposited silicon nano-particles. The fabric may for instancecomprise woven cotton yarns although the structure of the fabric may beformed from any other suitable natural or man-made textile elementsincluding for instance polyester, nylon, cotton, silk, viscose rayon,wool, linen, or any blend or composite structure thereof. Copperparticles are coated on to the fabric, for instance, in accordance withany of the embodiment processes described herein. It would beappreciated that the copper particles may be coated directly on to thewoven textile elements forming the fabric after the fabric has beenformed, however, the copper particles may be coated on to the textileelements (yarns, fibers etc), before the textile elements have beenformed into the fabric by weaving or any other suitable fabric formationtechnique. Silicon nano-particles are deposited on to the surfacestructure of the electrically-conductive textile elements of the fabricsuch that the silicon nano-particles encapsulate the surface structureof the fabric and/or are entangled within the yarns of the fabric. Asupersonic beam may be utilised during deposition of the siliconnano-particles on to the fabric in seeking to assist in the depositionof the silicon nano-particles on to the fabric whereby the siliconnano-particles are trapped within pockets or other recesses formed inthe surface structure of the textile elements. Advantageously, a higherpercentage of deposition of the silicon nano-particles on to thecopper-coated fabric will result in greater energy storage capacity ofthe anodic element. Also, because the silicon nano-particlesencapsulate, penetrate and are entangled within and/or between thesurface structures of the electrically-conductive textiles of the fabricsubstrate as shown in FIGS. 22 and 23, this alleviates damage due toexpansion of silicon during battery charging. For instance, cracking inthe silicon nano-particle coating is alleviated which makes it moredifficult for moisture to penetrate and damage the encapsulatedelectrically-conductive textile elements of the anode.

It would be understood that these embodiments of the present inventionare not limited to the example structures and geometries of the fabricor textile elements described herein and may take the form of othersuitable structure and geometries of the fabric of textile elementswithout departing from the spirit of the present invention. Forinstance, in alternate embodiments, a fabric may be provided comprisingfirst conductive fibres having a first type of particle depositedthereon (for instance n-type silicon nano-particles), and, secondconductive fibres having a different type of particles deposited thereon(for instance p-type silicon nano-particles) may then be wrapped aroundthe first conductive fibres, or vice versa. Between the first and secondconductive fibres of this composite-type yarn, there may be provided alayer to assist in facilitating electron and hole transfer to close thecircuit between the first and second conductive fibres.

It is further envisaged that an electrically-conductive fabric formed inaccordance with any embodiments described herein may be utilised as amesh filter in the ball milling process when producing the silicon-nanoparticles. It is possible to configure the process such that siliconnano-particles of a certain diameters may readily pass through the meshstructure of the fabric in the normal course of the milling processwhilst silicon nano-particles of a desired diameter may be trapped onthe surface structure of the electrically-conductive fabric being usedas the mesh filter. Conveniently, this process provides a dual functionin terms of both filtering silicon nano-particles of certain diametersduring the milling process whilst simultaneously providing coating ofelectrically conductive fabrics with silicon nano-particles which maythereafter be used as substrates in various embodiments of the presentinvention.

It would be appreciated that embodiments of the present invention mayassist in providing at least one of the following advantages:

-   (a) a relatively simple, expedient and scalable process may be    provided by certain embodiments for producing solar-grade silicon    nano-particles compared to certain technologies and processes    currently available in the existing art;-   (b) a relatively cost-effective and scalable process may be provided    by certain embodiments for producing solar-grade silicon    nano-particles in comparison to certain technologies, and    consequently, the cost of manufacturing devices such as solar cells    and anodic materials of batteries which comprise silicon    nano-particles may therefore be reduced;-   (c) in the processes of the embodiments for producing nano-silicon    particles, the step of distillation advantageously creates pores    within the particle or ingot depending on the order in which the    steps of the processes are performed—that is

Sequence 1

-   -   (i) Alloy raw silicon with (distillable) alloying metal to form        alloy ingots;    -   (ii) Process the ingots (e.g. ball mill the ingots) into alloy        nano-particles of about 100 nm-150 nm;    -   (iii) Distil the alloying metals from the allow nano-particles        to produce the silicon nano-particles; and    -   (iv) Further ball mill the silicon nano-particles to break apart        the porous structure in surfaces of the silicon nano-particles.

OR

Sequence 2

-   -   (i) Alloy the raw silicon material with at least one alloying        metal to form alloy ingots;    -   (ii) Distill the alloy ingots to produce porous silicon ingots;        and    -   (iii) Process the porous silicon ingots to form silicon        nano-particles.    -   Moreover, by using different percentages of Mg or Zn        (distillable metals) in the alloy, it is possible to control the        porosity of the final nano-particles produced as exemplified by        the SEM and BET images/data drawings. These pores are        particularly useful as these pores reduce the expansion during        charging and discharging for instance when the silicon        nano-particles are being used as an anodic material of a        battery. The ability to controllably produce the pores on the        surfaces of the silicon nano-particles is also advantageous in        that the presence of such pores provides additional stiffness to        an anodic structure formed from such nano-particles. This is        analogous to the way in which an I-beam provides relatively        greater structural stiffness than a regular block of steel due        to its structure.

-   (d) an electrically-conductive substrate comprising    electrically-conductive textile elements coated by silicon    nano-particles may be utilised as a novel component in solar cell    devices which may improve impact resistance, ease of storage,    transportation, installation and replacement due to the flexibility,    compactness and reduced weight of the novel component which may be    conveniently folded, rolled up and/or stacked; and

-   (e) an electrically-conductive substrate comprising    electrically-conductive textile elements coated by silicon    nano-particles may be utilised as a novel anodic element of    rechargeable battery devices. Conveniently silicon nano-particles    may fill up and be trapped within the pockets, spaces and faults of    the surface structures of the electrically-conductive substrate,    and, may be trapped between the surface structures of adjacent    textile elements of the electrically-conductive substrate. The    ability of the silicon nano-particles to fill up and be trapped    within the surface structures of the electrically-conductive    textiles elements allows for a greater amount of silicon to be    provided in the anode element which thereby improves energy storage    capacity of the battery. Also, by virtue of the manner of    encapsulation of the electrically-conductive textile elements by the    silicon nano-particles, problems (such as cracking) associated with    expansion of the silicon nano-particles during charging of the    battery may be alleviated. This solution teaches away from existing    approaches as it does not seek to reduce the amount of silicon in    the anode element and thus does not compromise the potential storage    capacity of the battery, and, this solution does not seek to only    partially charge the battery to alleviate silicon expansion and thus    does not encourage inefficient usage of the potential storage    capacity of the battery.

It would be understood and appreciated that the process of making theanode may well be extended to the making of the cathode, thus making aflexible battery with relatively higher energy storage capacity andlighter weight compared to traditional batteries.

Those skilled in the art will appreciate that the invention describedherein is susceptible to variations and modifications other than thosespecifically described without departing from the scope of theinvention. All such variations and modification which become apparent topersons skilled in the art, should be considered to fall within thespirit and scope of the invention as broadly hereinbefore described. Itis to be understood that the invention includes all such variations andmodifications. The invention also includes all of the steps andfeatures, referred or indicated in the specification, individually orcollectively, and any and all combinations of any two or more of saidsteps or features.

The reference to any prior art in this specification is not, and shouldnot be taken as, an acknowledgment or any form of suggestion that thatprior art forms part of the common general knowledge.

1. A process for producing silicon nano-particles from a raw siliconmaterial, the process including steps of: (i) alloying the raw siliconmaterial with at least one alloying metal to form an alloy; (ii)processing the alloy to form alloy nano-particles; and (iii) distillingthe alloying metal from the alloy nano-particles whereby siliconnano-particles are produced.
 2. A process as claimed in claim 1 whereinstep (ii) includes forming alloy particles having diametersapproximately in the range of 100 nm-150 nm.
 3. A process as claimed inclaim 1 wherein step (ii) includes ball milling the alloy to form thealloy nano-particles.
 4. A process as claimed in claim 3 wherein step(ii) is performed in a controlled environment to alleviate oxidisationof the alloy nano-particles and/or alleviate explosion due to pressurebuild-up within the milling chamber.
 5. A process as claimed in claim 4wherein the controlled environment includes a milling chamber in whichthe alloy is being ball milled with at least one of an inert gas, oil,diesel, kerosene and dehydrated ethanol filling disposed in the millingchamber.
 6. A process as claimed in claim 1 wherein the alloy is in aliquid form and step (ii) includes atomisation of the alloy to form thealloy nano-particles.
 7. A process as claimed in claim 1 wherein step(iii) includes distilling the alloying metal from the alloynano-particles in a vacuum furnace.
 8. A process as claimed in claim 1wherein the silicon nano-particles produced in accordance with step(iii) include diameters of approximately around 50 nm-150 nm.
 9. Aprocess as claimed in claim 1 including a further step following step(iii), including subjecting the silicon nano-particles to a furthermilling process in a controlled environment to break apart a porousstructure comprised by the nano-silicon particles.
 10. A process asclaimed in claim 1 wherein the alloying metal includes at least one ofzinc and magnesium.
 11. An apparatus for producing siliconnano-particles from a raw silicon material, the apparatus including: anapparatus for alloying the raw silicon material with at least onealloying metal to form an alloy; an apparatus for processing the alloyto form alloy nano-particles; and an apparatus for distilling thealloying metal from the alloy nano-particles whereby siliconnano-particles are produced.
 12. An apparatus as claimed in claim 11wherein the apparatus for processing the alloy to form the alloyparticles is configured to form alloy nano-particles having diametersapproximately in the range of 100 nm-150 nm.
 13. An apparatus as claimedin claim 11 wherein the apparatus for processing the alloy to form thealloy particles includes a ball milling apparatus having a millingchamber in which the alloy particles are able to be ball-milled in acontrolled environment to alleviate oxidisation of the alloynano-particles.
 14. An apparatus as claimed in claim 13 wherein thecontrolled environment includes the milling chamber in which the alloyis being ball milled having at least one of an inert gas, oil, diesel,kerosene and dehydrated ethanol disposed therein.
 15. An apparatus asclaimed in claim 11 wherein the apparatus for processing the alloy toform the alloy nano-particles includes an apparatus for performingatomisation of the alloy when in a liquid form.
 16. An apparatus asclaimed in claim 11 wherein the apparatus for distilling the alloyingmetal from the alloy nano-particles to produce the siliconnano-particles includes a vacuum furnace.
 17. An apparatus as claimed inclaim 11 wherein the apparatus for distilling the alloying metal fromthe alloy nano-particles to produce the silicon nano-particles isconfigured to produce silicon nano-particles having diameters ofapproximately around 50 nm-150 nm.
 18. An apparatus as claimed in claim11 wherein the apparatus is further configured for subjecting thesilicon nano-particles to a further milling process in a controlledenvironment to break apart a porous structure comprised by thenano-silicon particles.
 19. An apparatus as claimed in claim 11 whereinthe alloying metal includes at least one of zinc and magnesium.
 20. Asolar cell device for use in converting solar energy to electricalcurrent, the solar cell device including: a photosensitive elementcomprising an n-type layer contiguously connected with a p-type layer ata junction region therebetween, the n-type layer and contiguouslyconnected p-type layer of the photosensitive element being configuredsuch that, in response to the photosensitive element being exposed tosolar energy, free electrons are able to be released by thephotosensitive element so as to provide current flow through a loaddevice forming an external electrical circuit between the p-layer andn-layer of the photosensitive element; wherein said n-type layer andsaid p-type layer include at least one electrically-conductive substratehaving silicon nano-particles deposited on a surface structure of the atleast one electrically-conductive substrate. 21.-75. (canceled)